JPH0579502A - Hydraulic construction machine - Google Patents

Abstract

PURPOSE:To improve fine operability and responsiveness of an actuator at build up from stand-by flow by preparing two kinds, mild and quick, of control characteristics of a variable delivery pump to vary due to load sensing control, and selecting either one due to judgement of an operator. CONSTITUTION:When control valves 8, 9 are set neutral, by setting a responsive speed selecting switch 40 to a standard mode selecting position 41, the tilting rotational speed control part of a controller 74 is set to have a small gain at selection signal OFF. When an operation lever 18 is operated in this condition, load sensing control to hold the discharge pressure of a pump 2 higher than maximum load pressure by a decided pressure difference is performed so as to mildly operate an actuator 7. Meanwhile, when the switch 40 is changed over to the quick mode selecting position 42, the controller 74 is set to have a large gain at selection signal ON. When the operation lever is quickly operated in this condition, load sensing control toward target pump flow is performed so as to quickly operate the actuator 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic construction machine represented by a hydraulic excavator, a wheel loader, etc.
The present invention relates to a hydraulic construction machine equipped with a pump control device capable of controlling a displacement volume of a hydraulic pump driven by a prime mover according to an operation amount of an operation lever.

[0002]

2. Description of the Related Art In hydraulic construction machines such as hydraulic excavators and hydraulic cranes, the displacement volume of a hydraulic pump driven by a prime mover (in the case of a swash plate pump, the tilt amount of the swash plate) is the operation amount of an operating lever. A pump control device that controls according to the above is used, and as the pump control device, there are a load sensing control system and a negative control system. Load sensing control is, for example, DE-A.
1-342265 (JP-A-60-11706 or U.
(Corresponding to SP4, 617, 854), JP-A-2-2914
As disclosed in Japanese Patent No. 36, the maximum load pressure of a plurality of hydraulic actuators is detected, and the displacement volume of the hydraulic pump is controlled so that the discharge pressure of the hydraulic pump becomes higher than this maximum load pressure by a certain value. Therefore, the discharge amount of the hydraulic pump can be increased / decreased according to the load pressure of the hydraulic actuator, thereby saving energy and improving operability.

The negative control is to detect a pilot pressure signal related to the operation amount of the operation lever,
The displacement volume of the hydraulic pump is controlled according to this signal. When the operation lever is in neutral, the displacement volume of the hydraulic pump is controlled to the minimum value, and the displacement volume is increased as the operation lever is operated. This is a control method, which can also save energy and improve operability.

[0004]

However, the conventional hydraulic construction machine equipped with the above system has the following problems.

In the load sensing control system and the negative control system, since the displacement volume of the hydraulic pump is controlled according to the operation amount of the operation lever as described above, when the operation lever is in the neutral position, the displacement of the hydraulic pump is suppressed. The shelter volume is reduced to a preset minimum value. In this case, the discharge pressure of the hydraulic pump is maintained at a pressure higher than the tank pressure by a predetermined value by the unload valve, and the pump displacement volume at this time is usually set sufficiently small to reduce fuel consumption and improve fine operability. Is. In such a configuration, when the operation lever is suddenly operated from the neutral position,
The pump displacement volume increases with the lever operation amount,
Since the initial position of the pump displacement volume is small and the initial pump discharge flow rate (standby flow rate) is small, it takes time to reach the pump displacement volume according to the lever operation amount, and the responsiveness of the actuator deteriorates.

An object of the present invention is to provide a hydraulic construction machine which improves both fine operability and responsiveness of the hydraulic actuator when rising from the standby flow rate.

[Means for Solving the Problems]

According to a first aspect of the present invention, a variable displacement hydraulic pump driven by a prime mover, at least one hydraulic actuator driven by discharge oil from the hydraulic pump, and discharge oil from the hydraulic pump are provided. A hydraulic construction machine comprising a control valve leading to an actuator, operating means for controlling the stroke amount of the control valve, and pump control means for controlling the displacement volume of the hydraulic pump according to the operating amount of the operating member. Applied. And (a) first means for selecting a command value of the response speed of the actuator by an operator's operation and outputting a corresponding selection signal; (b) for the selection signal from the first means, The above object is achieved by including: a second means for switching the changing speed of the displacement volume of the hydraulic pump, which is controlled according to the operation amount of the operation means.

In the hydraulic construction machine according to claim 1, preferably, the pump control means detects a differential pressure between the discharge pressure of the hydraulic pump and the load pressure of the actuator, and the detected differential pressure and the differential pressure in advance. A means for calculating a deviation from the set target differential pressure, calculating a first target displacement volume change amount from the differential pressure deviation, and calculating a target displacement volume for keeping the detected differential pressure constant. The second means includes means for calculating a second target displacement volume change amount from the differential pressure deviation, and the first target displacement volume change amount and the second target displacement volume variation amount corresponding to the selection signal. And means for selecting one.

The pump control means detects a differential pressure between the discharge pressure of the hydraulic pump and the load pressure of the actuator, and obtains a deviation between the detected differential pressure and a preset target differential pressure. Means for calculating a first target displacement volume change amount from the pressure deviation to calculate a target displacement volume for keeping the detected differential pressure constant, and the second means outputs the selection signal to the selection signal. It may be configured to include means for outputting a correction coefficient of a corresponding level, and means for calculating a final target displacement volume by multiplying the target displacement volume by the correction coefficient.

According to a fourth aspect of the present invention, a variable displacement hydraulic pump driven by a prime mover, at least one hydraulic actuator driven by discharge oil from the hydraulic pump, and discharge oil from the hydraulic pump are provided. A control valve leading to an actuator, an operating means for controlling the stroke amount of the control valve, and a pump control means for controlling the displacement volume of the hydraulic pump are provided, and at least the operating means is at a neutral position. In some cases, it is applied to a hydraulic construction machine in which the displacement volume of the hydraulic pump is controlled so that the initial displacement volume is smaller than the displacement volume controlled when the operating means is operated. .. Then, there are provided at least two kinds of initial displacement volumes which can be set when the operating means is in the neutral position, and the first means for outputting a selection signal for selecting the initial displacement volume by the operation of the operator; The above-described object is achieved by including a selecting unit that selects one of the two types of initial displacement volumes in response to the selection signal output from the first unit.

[0011]

According to the invention of claim 1, in response to the selection signal from the first means, the mode is changed to a mode in which the changing speed of the displacement volume of the hydraulic pump controlled in accordance with the operation amount of the operation means is small. , The actuator works mildly,
Fine operability is improved. Further, when the mode in which the displacement speed of the displacement volume is large is switched to, the actuator operates quickly and the responsiveness is improved. According to the invention of claim 4, any one of the initial displacement volumes is selected according to the selection signal. Therefore, if a small initial displacement volume is selected according to the operator's preference and operation content, operation is started from a small standby flow rate when operating the operation means, the actuator is operated mildly, and fine operability is improved. improves. When a large initial displacement volume is selected, operation is started from a large standby flow rate when operating the operating means, the actuator is operated quickly,
Responsiveness is improved.

[0012]

【Example】

-First Embodiment- A first embodiment of the present invention will be described with reference to FIGS. In the first embodiment, the hydraulic pressure that performs the load sensing control (hereinafter, also referred to as LS control) and the input torque control that limits the maximum value of the pump displacement so that the pump input torque does not exceed the engine output torque. The present invention is applied to a construction machine, and two types of change speed characteristics of a target displacement volume that fluctuates by load sensing control are prepared, and either one can be selected by an operator's judgment.

Referring to FIG. 1, a hydraulic system relating to the hydraulic construction machine of the present embodiment includes a prime mover, that is, an engine 1,
The variable displacement hydraulic pump 2 driven by the engine 1 and the hydraulic pump 2 are connected to the hydraulic pump 2 in parallel via the discharge conduit 3 and the main circuit lines 4 and 5, and the discharge oil from the hydraulic pump 2 A plurality of driven hydraulic actuators 6 and 7 are provided, and the main pipeline lines 4 and 5 between the hydraulic pump 2 and the hydraulic actuators 6 and 7 have a flow rate of pressure oil supplied from the hydraulic pump 2 to the hydraulic actuators. Control valves 8 and 9 for controlling the supply direction are respectively connected, and pressure compensating valves 10 and 11 are connected upstream of the control valves 8 and 9.

In this embodiment, the hydraulic construction machine is shown in FIG.
The wheel type hydraulic excavator shown in FIG. 2 is symmetrical, the actuator 6 of the hydraulic system is a traveling motor that drives the rear wheel 50 via the transmission 51 and the propeller shaft 52, and the actuator 7 is a part of the front attachment 53, for example. A boom 5
4 is a boom cylinder that moves up and down.

The control valves 8 and 9 are pilot hydraulic type valves in the illustrated embodiment, and have pilot lines 55a and 55b.
And 56a, 56b are controlled by the pilot pressure.

The pilot lines 55a and 55b are shown in FIG.
It is connected to the traveling pilot circuit 57 shown in FIG.
The traveling pilot circuit 57 has a pedal-operated pilot pressure reducing valve 58 for instructing traveling speed and a manually operated directional switching valve 59 for instructing traveling forward and backward. Stepping on the pilot pressure reducing valve 58, the direction switching valve 59
To any position, the pilot pressure reducing valve 58
Then, a pilot pressure corresponding to the amount of depression is generated based on the pressure oil from the pilot pump 60, and this pilot pressure is transmitted through the slow return valve 61 to whichever of the pilot lines 55a and 55b, depending on the switching position of the direction switching valve 59. The control valve 8 is controlled in its opening degree and switching position according to the depression amount of the pressure reducing valve 58 and the switching position of the direction switching valve 59. When the depression of the pilot pressure reducing valve 58 is released, the pilot pressure is gradually reduced via the slow return valve 61, and the control valve 8 also gradually returns to the neutral position.

The pilot lines 56a and 56b are connected to a pilot valve having an operating lever 18 for instructing the speed and driving direction of the boom cylinder 7, and in the pilot valve, pilot pressure corresponding to the operating amount and operating direction of the operating lever 18 is used. Occurs, and this occurs in the pilot line 56a,
It is transmitted to the control valve 9 via 56b, and the opening degree and the switching position of the control valve 9 are controlled.

The pressure compensating valves 10 and 11 operate in response to the differential pressures across the control valves 8 and 9, respectively, regardless of changes in the discharge pressure of the hydraulic pump 2 and the load pressures of the hydraulic actuators 6 and 7. By keeping the differential pressure across the valves 8 and 9 constant, it is possible to secure a flow rate according to the opening of the control valves 8 and 9.

The control valves 8 and 9 have load lines 12 and 1 for detecting the load pressures of the actuators 6 and 7, respectively.
3, the load lines 12 and 13 are further connected to the load line 14 via the high pressure selection valve 19, and the high pressure selection valve 1
The load pressure on the high-pressure side selected in 9, that is, the maximum load pressure is introduced to the load line 14.

The load pressure detected in the load lines 12 and 13 on the input side is transmitted to the pressure compensating valves 10 and 11 described above, and the maximum load pressure detected in the load line 14 is transferred to the unload valve 16.
Be led to.

The engine 1 is preferably a diesel engine equipped with a fuel injection device 30 with an all-speed governor. The fuel injection device 30 has a governor lever 31, and the governor lever 31 is driven by a pulse motor 35.

The hydraulic pump 2 is a swash plate pump, and the regulator 75 controls the swash plate position, that is, the tilt angle (pump displacement). The regulator 75 is
It has two electromagnetic valves 76 and 77, and a servo cylinder 78 whose position is controlled by controlling the supply and discharge of pressure oil by switching the electromagnetic valves. The servo cylinder 78 drives the swash plate of the hydraulic pump 2. It In addition, the response speed selection switch 40 that selects the command value of the response speed of the actuators 6 and 7 by the operator's operation and outputs the corresponding selection signal S
Is provided. Response speed selection switch 40 is terminal 4
When it is 1, the standard mode is selected, the selection signal S is OFF at this time, and when switched to the terminal 42, the quick mode is selected and the selection signal S is turned ON.

The engine 1 and the hydraulic pump 2 are also provided.
In order to control the above, the tilt angle sensor 70 for detecting the tilt angle (pushing capacity) θs of the swash plate of the hydraulic pump 2, the pressure sensor 71 for detecting the discharge pressure Pp of the hydraulic pump 2, the hydraulic pump 2
Differential pressure sensor 33 for detecting the differential pressure ΔPLS between the discharge pressure of the engine and the maximum load pressure of the actuators 6, 7, a rotational speed sensor 73 for detecting the rotational speed of the engine 1, and a potentiometer for detecting the amount of rotation of the governor lever 31. A sensor group consisting of a switch 34. Further, a fuel lever 32 that is manually operated by an operator and outputs an electric signal of a level corresponding to the displacement amount is provided, and signals from the sensor group, the fuel lever 32 and the switch 40 are sent to a controller 74 mainly composed of a microcomputer. Is entered.

The controller 74 has an engine control function and a pump control function. In the engine control function, a target rotation speed of the engine 1 is set according to a signal from the fuel lever 32, and the target rotation speed is set. A drive signal is output to the pulse motor 35 so that the target rotation speed can be obtained from the target displacement amount of the governor lever 31 and the actual displacement amount of the governor lever 31 detected by the potentiometer 34.

In the pump control function, the controller 74 has a tilt angle sensor 70, a pressure sensor 71, a differential pressure sensor 33, a rotation speed sensor 73, and a potentiometer 3.
4. Input a signal from the response speed selection switch 40 and output a drive signal to the solenoid valves 76 and 77 of the regulator 75. Then, the load sensing control for controlling the tilt angle of the hydraulic pump 2 is performed so that the discharge pressure of the hydraulic pump 2 becomes higher than the maximum load pressure by a constant pressure difference, and the input torque of the hydraulic pump 2 becomes equal to that of the engine 1. Input torque limit control is performed to control the tilt angle of the hydraulic pump 2 so that the output torque falls within the output torque range.

The unload valve 16 is set so that the discharge pressure of the hydraulic pump 2 is slightly higher than the set differential pressure of the load sensing control when the control valves 8 and 9 are in the neutral position.
As a result, the pump tilt angle when the control valves 8 and 9 are in the neutral position is maintained at the minimum tilt angle.

Details of the pump control function of the controller 74 will be described with reference to FIG. The pump control function of the controller 74 includes a load sensing (LS) control unit 85, a torque control unit 86, a minimum value selection unit 87, and a servo control unit 88.

In the LS control section 85, the target differential pressure ΔPo and the actual differential pressure ΔPLS detected by the differential pressure sensor 33 (see FIG. 1).
The differential pressure Δ (PLS) with respect to the feedback value is calculated, and based on the differential pressure Δ (PLS), the first control gain setting unit 96 and the tilt speed control unit 95 change the target value ΔθL (= control speed). Is calculated and integrated to obtain a target pump tilt angle θL for LS control. The control gain K1 is set in the first control gain setting unit 96, and the differential pressure Δ (PLS)
And the control gain K1 from the first target value change amount ΔθL
1 is required.

The tilting speed control unit 95 has a second control gain setting unit 97, and a control gain K2 larger than the control gain K1 is set in the second control gain setting unit 97,
From the differential pressure Δ (PLS) and this control gain K2, the second target value change amount Δθ that is larger than the first target value change amount ΔθL1.
L2 is required. Further, the tilt speed control unit 95 is provided with a switch 98, and the switch 98 outputs the first target value change amount ΔθL1 when the selection signal S from the response speed selection switch 40 (see FIG. 1) is OFF. When the selection signal S is ON, the second target value change amount ΔθL2 is output.

In the torque control unit 86, the margin torque ΔT is calculated from the deviation between the engine speed Nr detected by the speed sensor 73 and the governor lever displacement amount (control speed) Nθ detected by the potentiometer 34. Then, speed sensing is performed, a target torque Tpo for preventing engine stall is calculated from the surplus torque ΔT, and the target torque Tpo is multiplied by the reciprocal 1 / Pp of the pump discharge pressure Pp detected by the pressure sensor 71. A calculation is performed and the obtained value θps is filtered by a first-order lag element to obtain a target pump tilt angle θA for input torque limit control.

In the minimum value selection unit 87, the minimum value of the target pump tilt angle θL from the LS control unit 85 and the target pump tilt angle θA from the torque control unit 86 is selected as the tilt angle command value θr. In the servo control unit 88, the difference Δθ between the tilt command value θr and the feedback value θs of the actual tilt angle detected by the tilt angle sensor 70 is calculated, and this difference Δθ is calculated.
Is a predetermined value of the dead zone or more, a drive signal for driving the solenoid valves 76, 77 is output.

In the above structure, when the operating lever 18 and the pilot pressure reducing valve 58 (see FIG. 3) are in the neutral position and the control valves 8 and 9 (see FIG. 1) are in the neutral position,
If the response speed selection switch 40 (see FIG. 1) is set to the standard mode selection position of the terminal 41, the selection signal S becomes OF.
At F, the tilting speed control unit 95 selects the first target value change amount ΔθL1 as the target value change amount ΔθL. Therefore, if the operator operates the operation lever 18 from this state, the target pump tilt angle θL of the LS control is selected by the minimum value selection unit 87, and the flow rate increases with the first target value change amount ΔθL1 as the change speed. In addition, load sensing control is performed in which the pump discharge pressure is kept higher than the maximum load pressure by a constant differential pressure ΔPo. Therefore, at this time, the pump discharge flow rate gradually increases, and the actuator 7 operates mildly. Further, when the target pump tilt angle θA for torque control is selected by the minimum value selection unit 87, input torque limit control is performed so that the input torque of the hydraulic pump 2 does not exceed the output torque of the engine 1. ..

On the other hand, when the operation lever 18 and the pilot pressure reducing valve 58 are in the neutral position and the control valves 8 and 9 are in the neutral position, when the response speed selection switch 40 is switched to the quick mode selection position of the terminal 42, the selection signal. S is turned on, and the tilting speed control unit 95 selects the second target value change amount ΔθL2 (> ΔθL1) as the target value change amount ΔθL. Therefore, when the operator suddenly operates the operation lever 18 in this state, if the target pump tilt angle θL of the LS control is selected by the minimum value selection unit 87, the second
The flow rate is increased with the target value change amount ΔθL2 of (1) as the change speed, and the load sensing control is performed as described above. Therefore, the actuator 7 quickly reaches a desired speed and the responsiveness is improved.

Further, the target pump tilt angle θ for torque control
If A becomes smaller than the target pump tilt angle θL for LS control, in this case, the former target pump tilt angle θA is selected by the minimum value selection unit 87, and the hydraulic pump 2 limits the input torque as described above. Controlled.

As described above, according to the present embodiment, the changing speed of the tilt angle of the hydraulic pump 2 can be changed by switching the response speed selecting switch 40. Therefore, in a mode in which the changing speed is small, the actuator is operated mildly. In addition, the operability can be improved, and the actuator can be activated quickly in the mode in which the change speed is large, and the responsiveness can be improved.

Further, in this embodiment, since the tilting speed control is performed in combination with the input torque limit control, even if the second control gain K2 set in the setting section 97 is set to a considerably large value. , The engine 1 (see FIG. 1) never becomes overtorque.

-Second Embodiment-In place of the response speed selection switch 40 of the two-position switching system used in the first embodiment, an electric signal of a level corresponding to the operation amount such as a dial type variable volume is selected. An operation member that outputs as the signal S can also be used. That is, FIG.
As shown in, the tilting speed controller 95 of the LS controller 85A.
A is provided with a setting unit 99 that sets a correction coefficient K3 that increases according to the level of the electric signal, and a calculation unit 100 that multiplies the target value change amount ΔθL1 from the gain setting unit 96 and the correction coefficient K3. The value obtained by the unit 100 may be used as the final target value change amount ΔθL to perform an integral calculation to obtain the target pump displacement angle θL for LS control. As a result, the changing speed of the pump tilt angle can be arbitrarily changed, and the responsiveness when switching the operation lever can be arbitrarily adjusted.

The method for controlling the pump tilt angle so that the tilt angle of the hydraulic pump increases in accordance with the operation amount of the operating device is limited to the LS control method described above. However, for example, in an operation method in which the operation amount of the operation lever is transmitted to the control valve by a rod, there are various other methods such as a so-called external compensating control system that controls the pump tilt angle by following the movement of the rod. Even if adopted, the same effect can be obtained.

-Third Embodiment- FIG. 6 and FIG. 7 are views showing a third embodiment. In the third embodiment, the minimum pump tilt angle during the known negative control can be arbitrarily changed. The same parts as those in FIGS. 1 and 3 are designated by the same reference numerals for description.

In FIG. 6, the hydraulic system of this embodiment includes an engine 301, a variable displacement hydraulic pump 302 driven by the engine 301, and a traveling motor 6 driven by oil discharged from the hydraulic pump 302. ,
The boom drive hydraulic cylinder 7, the arm drive hydraulic cylinder 305, and the control valves 306, 307, 308 for controlling the flow rate and the supply direction of the pressure oil supplied from the hydraulic pump 302 to each hydraulic actuator are provided. Control valve 306-
A center bypass line 310 connected to the discharge line 309 of the hydraulic pump 302 penetrates through 308, and the control valves 306 to 308 respectively fully open the flow path of the center bypass line 310 in the neutral position, and the control valve 306 to 308 respectively. The flow path is configured to be narrowed as it is operated from the position to the operating position.

A negative control valve 320 is connected to the most downstream end of the center bypass line 310. Negative control valve 3
Reference numeral 20 denotes a relief valve 32 that generates a negative control pressure of a negative control pilot line 312 that is connected to a pilot pump 311 that is also driven by the engine 301.
1 and a pressure adjusting valve 322 that acts on the spring 321a of the relief valve 321 to adjust the set pressure.

As shown in FIG. 7, the preset value of the spring 321a can be adjusted steplessly by the external operation switch 330, so that the relief set pressure of the relief valve 321 can be adjusted.

In the thus constructed negative control valve 320, when the pressure is rising in the center bypass line 310, the adjusting valve 322 sets the relief pressure of the relief valve 321 to the maximum, and the negative control pressure of the pilot line 312 becomes Maintained at maximum. When the pressure in the center bypass line 310 decreases, the adjusting valve 32 is accordingly
2 reduces the set pressure of the relief valve 321 and reduces the negative control pressure of the pilot line 312.

The tilt angle of the hydraulic pump 302 is adjusted by the pump regulator 313. Pump regulator 3
Reference numeral 13 controls the pump displacement volume in the same manner as the input torque control unit described above. The discharge pressure of the hydraulic pump 302 is guided to this torque control unit via a pilot line 314 for torque control branched from the discharge pipe line 309 of the hydraulic pump 302, and the input torque of the hydraulic pump 302 is the output torque of the engine 301. The input torque limit control is performed so as to be within the range. The pump regulator 313 also has a negative control unit, and the negative control valve 32 is connected to the negative control unit via the negative control pilot line 312.
The negative control pressure generated at 0 is introduced. When the negative control pressure is maximum, the pump displacement angle is kept to a minimum, and the pump displacement angle is controlled so as to increase as the negative control pressure decreases.

The control valve 306 is pilot-controlled by an operating device 57 having a pilot pressure reducing valve 58, and the control valve 3
07 and 308 are pilot-controlled by an operating device provided with operating levers and 303.

In the hydraulic system constructed as described above, the center bypass line 310 and the negative control valve 32 are provided.
0, the negative control pilot line 312, and the negative control section of the pump regulator 313 constitute a negative control system.

Pilot pressure reducing valve 58 and operating lever 1
Control valves 306-30
When all 8 are in the neutral position, the center bypass line 310 is fully opened and the center bypass line 310 is opened.
The discharge pressure at the minimum tilt position of the hydraulic pump 302 rises, the negative control valve 320 maintains the negative control pressure of the pilot line 312 to the maximum as described above, and the hydraulic control 302 of the negative control of the pump regulator 313 is controlled. The tilt angle of is kept to a minimum.

When the preset value of the spring 321a of the relief valve 321 is reduced by the external operation switch 330, the negative control pressure of the pilot line 312 is reduced by the preset value when the control valves 306 to 308 are not operated. descend. As a result, the control valve 306-
When 308 is not operated, the variable displacement hydraulic pump 302
The tilt angle of is larger than that before the preset value is changed, and the standby flow rate is set to a large value. On the contrary, the spring 321a
When the preset value of is increased, the control valves 306 to 308
When is not operated, the tilt angle of the variable displacement hydraulic pump 302 is smaller than that before the preset value is changed, and the standby flow rate is set to be small.

When any one of the control valves 306 to 308 is operated, the corresponding control valve is operated and moved from the neutral position, and the center bypass line 31 is correspondingly operated.
0 is gradually narrowed down. As a result, the pressure of the center bypass line 310 decreases, the set pressure of the negative control valve 320 also decreases, and the negative control pressure of the pilot line 312 gradually decreases. Therefore, the pump tilt angle controlled by the negative control unit of the pump regulator 313 gradually increases.

In this way, the pump regulator 31
The negative control unit 3 controls the pump tilt angle according to the operation amount of the operating device so that the tilt angle of the hydraulic pump increases as the operation amount increases. Further, the standby operation flow rate can be arbitrarily changed by the external operation switch 330.

Therefore, according to the third embodiment, if the negative control pressure when the operating device is in the neutral position is set low by operating the external switch 330, the hydraulic pump 30
The standby flow rate of 2 can be increased, and when the operating device is suddenly operated, the actuator can be activated quickly and the responsiveness can be improved. If the negative switch pressure when the operating device is in the neutral position is set to a high value by the external switch 330,
The standby flow rate of the hydraulic pump 302 can be reduced, and when operating the operating device, the actuator can be mildly operated to improve fine operability. A method of mechanically adjusting the preset value of the spring 321a may be adopted.

[0052]

According to the present invention, since the changing speed of the pump displacement volume can be changed, the actuator operates mildly in the mode in which the changing speed of the pump displacement volume is small, the fine operability is improved, and the pump displacement is improved. In the mode in which the change speed of the shelter volume is large, the actuator operates quickly and the responsiveness is improved. Further, according to the present invention, since the standby flow rate at the time of negative control can be changed, the standby flow rate can be set large to improve the responsiveness, and the standby flow rate can be set small to improve the fine operability. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a hydraulic system of a hydraulic construction machine according to a first embodiment of the present invention.

FIG. 2 is a side view of a wheel hydraulic excavator which is a hydraulic construction machine equipped with the hydraulic system shown in FIG.

3 is a schematic view of an operating device of the hydraulic system shown in FIG.

4 is a block diagram showing a pump control function of the controller shown in FIG. 1. FIG.

FIG. 5 is a block diagram showing a pump control function of the second embodiment.

FIG. 6 is a diagram showing a hydraulic circuit of a third embodiment.

FIG. 7 is a diagram showing details of the negative control valve of FIG.

[Explanation of symbols]

1 prime mover 2 hydraulic pump 6,7 hydraulic actuator 8,9 control valve 18,59 operating means 40 response speed selection switch 74 controller 75 regulator 85 LS control unit 86 torque control unit 95,95A tilting speed control unit 96 1st
Control gain setting unit 97 second control gain setting unit 98 switch 99 setting unit 100 computing unit 320 negative control valve 330 operation switch

Claims (4)

[Claims] 1. A variable displacement hydraulic pump driven by a prime mover, at least one hydraulic actuator driven by discharge oil from the hydraulic pump, and a control valve for guiding the discharge oil from the hydraulic pump to the actuator. A hydraulic construction machine comprising: operating means for controlling the stroke amount of the control valve; and pump control means for controlling the displacement volume of the hydraulic pump according to the operating amount of the operating member. A first means for selecting a command value of the response speed of the actuator and outputting a corresponding selection signal by: (b) an operation of the operation means in response to the selection signal from the first means. A hydraulic construction machine, comprising: a second means for switching a changing speed of the displacement volume of the hydraulic pump controlled according to the amount. 2. The hydraulic construction machine according to claim 1, wherein the pump control means detects a differential pressure between a discharge pressure of the hydraulic pump and a load pressure of the actuator, and the detected differential pressure is preset. And a means for calculating a first target displacement volume change amount from this difference in differential pressure and calculating a target displacement volume for keeping the detected differential pressure constant. The second means calculates a second target displacement volume change amount from the differential pressure deviation, and one of the first and second target displacement volume change amounts corresponding to the selection signal. And a means for selecting a hydraulic construction machine. 3. The hydraulic construction machine according to claim 1, wherein the pump control means detects a differential pressure between a discharge pressure of the hydraulic pump and a load pressure of the actuator, and the detected differential pressure is preset. And a means for calculating a target displacement volume change amount from this differential pressure deviation to calculate a target displacement volume for keeping the detected differential pressure constant, The second means includes means for outputting a correction coefficient having a level according to the selection signal, and means for calculating a final target displacement volume by multiplying the target displacement volume by the correction coefficient. Hydraulic construction machinery. 4. A variable displacement hydraulic pump driven by a prime mover, at least one hydraulic actuator driven by discharge oil from the hydraulic pump, and a control valve for guiding the discharge oil from the hydraulic pump to the actuator. And a pump control means for controlling the displacement of the hydraulic pump, and a pump control means for controlling the displacement volume of the hydraulic pump, the pump control means, at least when the operation means is in the neutral position, In the hydraulic construction machine configured to control the displacement volume of the hydraulic pump so that the initial displacement volume is smaller than the displacement volume set when the operating mechanism is operated, There are at least two types of initial displacement that can be set when in the neutral position. A first means for outputting a selection signal for selecting the product; and a selection means for selecting one of the two types of initial displacement volumes corresponding to the selection signal output from the first means. A hydraulic construction machine characterized by that.